Sensors that are used for engine control of an internal combustion engine must be monitored in order to ensure safety and emissions compliance during operation. A check must be made, inter alia, of the cooling water temperature sensor to determine whether it is stuck in a high temperature range and is thus continuously signaling too high a cooling fluid temperature.
It is known to monitor the signals of the cooling water temperature sensor in terms of signal limit values, using the control unit software. It is furthermore known to monitor whether, after an engine start, a minimum value is reached or a minimum signal change occurs (“dynamic plausibilization”).
It is known from German Patent Publication No. DE 101 20 968 to check during operation whether a change in the cooling water temperature occurs upon a transition from a low to a high load range. If not, a fault is reported.
German Patent Publication No. DE 44 26 494 discloses the monitoring of a cooling temperature sensor and of a thermostat by monitoring the change over time in the temperature sensor. If that change is too great, a fault is detected. The temperature behavior upon engine startup and under specific driving conditions, such as idling, is additionally checked, on the one hand based on typical rises in cooling temperature after engine startup, and on the other hand by means of a comparison with other signals.
With the methods of the existing art, it is not possible to monitor a sensor, in particular a temperature sensor, for a persistence in the high signal range or to identify this fault (“high side check”).
It is therefore the object of the present invention to describe a method that detects a persistence of a sensor, in particular a cooling water sensor, in the high signal range.